Nuclear reactors use a variety of damage prevention/mitigation devices and strategies to minimize the risk of, and damage during, unexpected or infrequent plant events. An important aspect of risk mitigation is prevention of plant damage and radioactive material escape into the environment caused by seismic events. Various seismic risk mitigation devices and analyses are used to ensure that the containment building is not breached, and that other plant damage is minimized, during seismic events.
A known seismic damage and risk mitigation device is a seismic bearing used in building foundations. FIG. 1A is an illustration of a conventional seismic bearing 10 useable in nuclear plants and other buildings and structures to reduce damage from earthquakes. As shown in FIG. 1A, seismic bearing 10 includes an upper plate 15 and lower plate 16 separated by an energy-absorbing and restorative core post 12, which may be surrounded by another similar material or materials, such as an elastic rubber annulus 11 and stiffening plates 13. Lower plate 16 may be attached to a building foundation or ground under the building, while upper plate 15 may be attached to the actual building structure.
As shown in FIG. 1B, when lower plate 16 vibrates or moves during an earthquake, the core post 12, annulus 11, and/or stiffening plates 13 may absorb vibratory energy and permit nondestructive relative movement between upper plate 15 and lower plate 16, and thus building and ground. Although conventional seismic bearing 10 is shown as a known rubber bearing design, other known core materials and resistive plate separators are useable therein. Any number of seismic bearings 10 may be used in combination at a base of a building in order to provide a desired level of seismic protection.